This invention pertains generally to pulse transmitters and receivers for radio frequency signals and particularly to such apparatus used at frequencies about 90 GHz.
Within the past few years improvements in solid state devices have made it feasible to exploit the window in the radio frequency spectrum at 94 GHz. Thus, intensive efforts have recently been undertaken to develop radar systems operating at 94 GHz for use where size is at a premium, as in guided projectiles or sub-munitions. In such an application, relatively small and light elements such as antennas and feeds may be utilized to achieve angular measurement capabilities which approach the capability of optical systems.
Unfortunately, however, the development of an active radar for use at 94 GHz has been hindered by the lack of adequate transmit-receive switches. Such a lack, in turn, has led heretofore to the requirement that separate antennas be provided for the transmitter and receiver. Such a requirement is, obviously, extremely detrimental when the system is to be used in a guided missile.
In addition, as is well known in the art, if a pulse Doppler radar is desired, the first local oscillator in the receiver must be arranged to maintain a known offset in frequency from the frequency of each transmitted pulse. That is to say, coherency between transmitted and received signals must be maintained to allow Doppler shifts to be determined.